This invention relates to the ink jet printing art. More particularly, this invention relates to a solution to the problem caused by horizontal movement of the ink jet print head during printing and the skewing of the printing pattern caused by that movement. Further, it is clearly more satisfactory to print in both directions of head travel than in just one direction of travel which requires a non-functioning return. However, printing in both directions of head travel requires a different skewing correction for left to right travel than for right to left travel.
The problem of compensation for the traveling motion of the ink jet head in printing for both directions of travel is discussed in U.S. Pat. No. 4,138,688. That patent shows an electronic system by which the electric field between the deflection plates is altered or distorted in a particular way to cause ink job droplets deposited on the printing media to be vertically aligned and to compensate for horizontal travel. However, the ink jet head and deflection plate system as shown in that patent is comparatively sophisticated and complex. It would be desirable to have a system of deflection plate electronics similar to that for unidirectional printing and yet useable for bi-directional printing.
Accordingly, this invention relates to the provision of a bi-directional ink jet printer in which a particular deflection plate system compensates for skewing in both directions of travel of the ink jet head by reversing the direction of ink jet scanning as head travel direction is reversed.